Defroster for evaporators



Dec. 27, 1949 p PETERSON 2,492,397

DEFROSTER FOR EVAPORATORS Filed Jan. 26, 1946 g 14 {Z 1: I I

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(Ittorneg Patented Dec. 27, .1949

DEFROSTER FOR EVAPORATORS Hans I. Peterson, Manchester, Comm, assignorto The Bush Manufacturing Company, Hartford,

Conn.

Application January 26, 1946, Serial No. 643,715

3 Claims.

This invention relates to a defroster for evaporators such as used onrefrigerating machinery, and more particularly for such evaporators ascomprise a plurality of layers, or rows, of cooling coils which arecommonly provided with radiating fins thereon.

Such evaporators, when used on refrigerating machinery, gather anaccumulation of frost which, when permitted to remain on the coils,greatly impairs the operation of the cooling or refrigerating systemunless the said frost is removed by a defrosting operation.

Heretofore, when defrosting evaporating coils by means of electricalenergy, it has been common practice to: (a) totally enclose theevaporator in an insulating chamber containing electrical heating units;defrosting taking place when the heaters have reached the temperature ofthe chamber above freezing. Such units are both cumbersome and expensiveto construct.

(b) To provide high intensity electric strip heaters under theevaporator coil, of which only a small percentage of their capacity isutilized in heating the coil and providing defrosting. The remainder ofthe heating capacity is spent for heating the refrigerated space andthis is highly undesirable.

It is an object of this invention, therefore, to provide a novel meansof defrosting evaporators through the application of low intensityelectrical heat, with a minimum of wastage, by direct conduction to theevaporator coils and to the frost on said coils, rather than byconvection which would cause wastage of heat between the heatingelements and the frost on the evaporators.

A further object of this invention is to distribute electrical energyover the coils by the use of inexpensive electrical heating cable, suchas connnonly found on the market, thus providing a unit that is compactin spacing requirement and ehicient in energy consumption.

It is a further object of this invention to provide a heating elementwhich is So constructed that, when placed in position relatively to thecoils of an evaporator, the said element will be in direct heatconducting relation to said coils and to the fins mounted thereon.

Further objects and advantages of this invention will be more clearlyunderstood from the following description and from the accompanyingdrawings, in which- Figure l is a perspective view of an evaporator coilshowing my invention as applied thereto.

Figure 2 is an end view thereof, in vertical section on line 2-2 of Fig.1.

Figure 3 is a fragmental view in central vertical section showing aportion of a heating element embodying my invention.

Figure 4 is an elevational plan view of one of my novel defrostingunits.

As shown in the drawings, the numeral 5 denotes an evaporator coil ofcommon construction having a pair of headers 6-6 between which areextended cooling tubes 1 through which the refrigerant flows for coolingthe said tubes. The fins 8 are provided on said tubes for radiation.

In the embodiment of my invention as shown,

I I provide defrosting means, preferably in the form of heating units 9,which may include electric heating element ofcommon form ,aifdpreferably comprising a tube Ill having embedded therein a resistanceelement II, in the'form of a coil, which is supported axially in saidtube by means of an insulating medium l2. The said tube is bent, asclearly illustrated in Fig. 2, and sandwiched between two sheets ofmeshed material l3-!3, preferably a wire mesh. This retains theformation of the heating element and also permits the insertion of saidelement between the different layers of coils'or tubes I in theevaporator unit.

As shown, one of said heating units maybe placed between each coil, orlayer, of tubes in theevaporator. As illustrated in Fig. l, theevaporator is in such a position that the, heating units are supportedtherein in a horizontal position.

The said heating units may be electrically con nected in parallel, orinseries as shown, by means of extensions M; the terminal ends -lEi-l5 ofthe heating units projecting from the ends of the outer units forconnection to a suitable electric current supply.

If desired, one or both of the lead ends 955 may be extended through adrain pipe is of a drip pan ll", located under the evaporator to catchliquid dripping therefrom, so that the said drain pipe may be kept freeof frost by the heat from the said heating elements as they are used fordefrosting the evaporator.

In the use of my invention, electric current may be supplied to theheating elements by any suitable means and the supply of current may beautomatically timed so that the evaporators will be defrosted atpredetermined intervals without requiring further attention.

When the said heating units are disposed hori zontally between thecoils, as in the application shown in Fig. 1, the liquid from themelting frost may be precipitated through the meshed wire sheets ill-43without obstruction from the said 3 heating units. Further, the mountingof the heating unit coils within the meshed material supports the saidheating units while still permitting free circulation of air through thecondenser.

It will be noted that, when the heating mem- 'bers are in operativeposition upon the coils or upon the fins on said coils, the wire mesh 9is in direct contact with all of said coils or fins and this serves toprovide for the direct conduction of heat from the heating elements tothe said coils or fins. Also, when frost has accumulated upon theevaporator, the said heating members will become practically embedded inthe front, thereby providing contact between the heating members and thefrost which will result in a greater degree of efiiciency from thedefrosting operation.

Further, the said heating elements are preferably of a low intensity,thereby permitting a more even distribution of heat per square foot ofevaporator surface area than would be provided with a-high intensityunit wherein the surface area closest to the heating elements wouldattain a much higher heat than the area removed from the said elements.

While I have shown my invention as applied to an evaporator of oneparticular form, it is to be understood that the same may be applied tocoolers and evaporators of different forms so as to cause defrostingthereof by direct heat conduction to the said coolers or evaporator-swithout departing from the scope of my invention, as set forth in theappended claims.

I claim:

1. In an evaporator or cooling unit comprising a plurality of layers ofcoils or tubes, a heating member positioned adjacent to said layers fordefrosting said unit; said heating member comprising a heating elementsupported by a. sheet of pervious material and retained in positionthere by between said layers.

2. In combination with an evaporator or cooling unit having a drip panlocated below said unit, for collecting liquid dripping therefrom, and adrain pipe for said pan; heating means comprising a heating elementdistributed within said unit for melting an accumulation of frostthereon; the said heating element extending also through said drain pipefor keeping the same clear of frost.

3. In an evaporator or cooling unit comprising a plurality of layers ofcoils or tubes; a heating member positioned adjacent to said layers fordefrosting said unit; said heating member comprising a heating elementsupported by a sheet of wire mesh and retained in position therebybetween said layers.

HANS P. PETERSON.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date Re. 18,263 Day Nov. 24, 19311,890,085 Hill Dec. 6, 1932 1,936,391 Harrower Nov. 21, 1933- 2,081,479Fink May 25, 1937 2,095,835 Rodman Oct. 12, 1937 2,185,692 McCleary Jan.2, 1940 2,196,291 Clancy Apr. 9, 1940 2,251,697 Van Daam et a1 Aug. 5,1941 2,262,336 Samuels Nov. 11, 1941 2,276,454 Becker Mar. 17, 19422,400,168 Roach s May 14, 1946 2,410,194 Baker Oct. 29, 1946

